Polypropylene

ABSTRACT

1. A PROCESS FOR THE PRODUCTION OF A SHAPED ARTICLE BY THE MELT EXTRUSION OF THERMALLY DEGRADED ISOTACTIC POLYPROPYLENE WHEREIN THE THERMAL DEGRADATION OF THE POLYPROPYLENE IS CARRIED OUT IN THE PRESENCE OF FROM 0.01 TO 5 PERCENT BY WEIGHT, BASED ON THE WEIGHT OF POLYPROPYLENE OF (A) AN ORGANOSILICON COMPOUND WHICH IS AN ORGANOSILANE OR ORGANOSILOXANE HAVING THEREIN AT LEAST ONE SILICONBONDED GROUP OF THE GENERAL FORMULA-CH2NR2, WHEREIN EACH R REPRESENTS A HYDROGEN ATOM OR A MONOVALENT HYDROCARBON RADICAL, 8B) AN ORGANOSILICON COMPOUND OF THE GENERAL FORMULA   1-(HO-),2-R&#34;,4-R&#34;&#39;&#39;,6-R&#39;&#39;-CYCLOHEXANE   WHEREIN R&#39;&#39;, R&#34; AND R&#34;&#39;&#39; EACH REPRESENT A HYDROGEN ATOM, AN ALKYL RADICAL HAVING UP TO 18 CARBON ATOMS, AN ARALKYL RADICAL HAVING UP TO 18 CARBON ATOMS OR A Q3SICH2GROUP, WHEREIN Q REPRESENTS AN ALKYL, ALKENYL OR ARYL RADICAL HAVING UP TO 18 CARBON ATOMS AT LEAST ONE OF R&#39;&#39;, R&#34; AND R&#34;&#39;&#39; BEING THE Q3SICH2- GROUP, OR (C) MIXTURES OF (A) AND (B).

United States Patent '0 Z POLYPROPYLENE William J. Owen and Bryan EwartCooper, Glamorgan, Wales, assignors to Midland Silicones Limited,Reading, England N Drawing..Original application July 20, 1970, Ser. No.56,659, now Patent No. 3,723,402, dated Mar. 27, v197d. Divided and thisapplication Apr. 26, 1972, Ser.

Int. Cl. C08f 29/02 US. Cl; 264-'211- 4 Claims ABSTRACT OF THEDISCLOSURE The production of shaped polypropylene articles by meltextrusion of .thermally degraded isotactic polypropylene can be carriedforward at lower temperatures than were heretofore required by.incorporating in the polypropylene prior to thermal degradation thereof,from 0.01 to percent by weight, based on the weight of thepolypropylene, or (a) a silane or siloxane having at least one ESlCHgNRgroup where R is hydrogen or a hydrocarbon radical, (b) an organosiliconcompound of the general formula wherein R, R" and R' are each a hydrogenatom, an alkyl radical of 1-18 carbon atoms, an aralkyl radical of lessthan 19 carbon'atoms or Q SiCH where Q is alkyl, alkenyl or aryl of lessthan 19 carbon atoms, at least one R, R or R' being Q SiCH or (c)mixture of (a) and (b).

quenching to drawing at elevated temperatures to orient the filament. Itis also known that filaments of polypropylene'having' high'tenacitiesmay be produced by degrading the polypropylene by drastic thermaltreatment, that is by exposure to temperatures of about 260 C. or above,prior to extrusion through the filament-forming orifice. The use of suchhigh temperatures however introduces considerable processingdifficulties since they approximate closely to the temperature at whichthe polypropylene chars and is rendered unsuitable for use. We have nowdiscovered that certain organosilicon compounds have the effect oflowering the temperature at which a given degree of degradation occursin polypropylene, thereby permitting the melt spinning of polypropyleneinto high tenacity fibres and filaments under less severe thermalconditions.

It is an object of this invention to introduce an improved method formelt extruding polypropylene. Another object is a method for meltextrusion of polypropylene wherein the required polypropylenedegradations can be carried forward at a lower temperature thanheretofore ice required. Other objects and advantages ofthe inventionare detailed in, or will be apparent from the disclosure and claimsfollowing.

This invention provides a process for the production of a shaped articleby the melt extrusion of thermallydegraded isotactic polypropylenewherein the thermal degradation of the polypropylene is carried out inthe presence of from 0.01 to 5% by weight based on the weight ofpolypropylene, of (a) an organosilicon compound which is an organosilaneor organosiloxane having at least one silicon-bonded group of thegeneral formula CH NR wherein each R represents a hydrogen atom or amonovalent hydrocarbon radical, (b) an organosilicon compound of thegeneral formula wherein R, R and R' each represents a hydrogen atom, analkyl radical having up to 18 carbon atoms, an aralkyl radical having upto 18 carbon atoms or a Q SiCH group, wherein Q represents an alkyl,alkenyl or aryl radical having up to 18 carbon atoms, at least one of R,R and R being the Q SiCH group, or (c) mixtures of (a) and (b).

In a further aspect the invention also includes a thermally-degradablecomposition comprising isotactic polypropylene and from 0.01 to 5% byweight of one or more of the specified organosilicon compounds (a) and(b).

As the organosilicon compound there can be employed any organosilane ororganosiloxane containing the grouping -CH NR bonded to at least onesilicon atom. In said group, each R represents a hydrogen a hydrogenatom or monovalent hydrocarbon radical, for example the methyl, ethyl,t-butyl, hexyl, octadecyl, vinyl, phenyl, tolyl or benzyl radical.Preferred as the organosilicon compounds (a) are the organosilanes andthe substantially linear polydiorganosiloxanes of low molecular weight,for example the di-, triand tetrasiloxanes having therein the specified-CH NR groups, any other substituents on the silicon atoms beingmonovalent hydrocarbon or halohydrocarbon radicals and oxygen atomspresent as siloxane (Si O Si) linkages.

Most preferably the organosilicon compounds (a) have the general formulan z zl 4-n wherein each A represents a radical having from 1 to 18carbon atoms and is a monovalent hydrocarbon radical, an alkoxy radical,an alkoxyalkyl radical, an alkoxyaryl radical or an alkoxyalkoxyradical, n is 0, 1, 2 or 3 but is preferbly 3 and R is as hereinabovedefined. As the A radicals in the general formula there may be presentone or more of alkyl radicals, for example methyl, ethyl, propyl, butyl,decyl, and octadecyl, alkenyl radicals such as vinyl and allyl and arylradicals such as phenyl, naphthyl, tolyl and benzyl. The A radicals canso comprise alkoxy radicals, for example methoxy, ethoxy and propoxyradicals for example radicals and alkoxyalkyl, alkoxyaryl andalkoxyalkoxy radicals for example methoxyethyl, ethoxypropyl,methoxyphenyl and methoxyethoxy radicals. Preferably however A is analkyl radical having less than 9 carbon atoms or a phenyl radical.

For optimum results it is believed that the organosilicon compoundsshould be compatible, at least to some extent, With the isotacticpolypropylene and some adjustment of the compatibility of the particulartype of compound chosen can be achieved by variation of the A radicals.

Some of the organosilicon compounds (a) employed in the process of thisinvention are well-known materials and others can be prepared accordingto the method described in U.S. Pat. No. 3,504,007.

f The organosilicon compounds (b) which can be employed to assist in thedegradation of polypropylene according to this invention may be broadlytermed as silylsubstituted phenols. They are more particularly describedby the general formula wherein R, R" and R each represents a hydrogenatom or an alkyl or aralkyl radical having up to 18 carbon atoms, forexample the methyl, ethyl, propyl, t-butyl, heyli, dodecyl, benzyl or2-phenyletiryl radical, or a Q SiCH group wherein each Q represents analkyl, alkenyl or aryl radical having having up to 18 carbon atoms. Atleast one of R, R and R should be the Q SiCH radical, examples of whichare the trimethylsilylmethyl diphenylmethylsilylmethyl,vinyldimethylsilylmethyl and dimethylbenzylsilylmethyl radicals. Thepreferred compounds (b) are those wherein the radicals represented by R,R", R and Q are selected from alkyl radicals having less than 9' carbonatoms and phenyl radicals.

Organosilicon compounds (b) can be prepared, for example, by thereaction in the presence of magnesium of a phenolic compound havingsubstituted therein a halomethyl group with an organosilicon compound QSiHal wherein Q is as hereinabove defined and Hal represents a halogenatom, preferably the chlorine or bromine atom. Such a method is morecompletely described in our copending US. application Ser. No. 752,790,filed Aug. 15th 1968.

When carrying out the process of this invention the organosiliconcompound can be introduced into the polymer by an suitable procedure.For example, a solvent solution or dispersion of the organosiliconcompound can be employed to coat granules of the polypropylene prior tomelting, or the organosilicon compound can be added directly to thepolypropylene melt. We have found that degradation of the polypropyleneto an extent suitable for performing the melt extrusion process can beachieved at temperatures of 230 C. or lower in the presence of theorganosilicon compound.

Although applicable in the production of any shaped article such assheets, by melt extrusion, the process of this invention findsparticular application in the formation of fibres and filaments ofpolypropylene by melt spinning. In common with known techniques thefibres or filaments can be quenched following spinning and are thensubjected to drawing at elevated temperatures to bring about orientationof the fibre or filament to provide the desired high tensile properties.

In addition to assisting the thermal degradation of polypropylene attemperatures above about 180 C. the organosilicon compounds (a) and (b)employed herein also function to stabilise the polypropylene againstoxidation at temperatures up to about 120150 C. The use of theorganosilicon compounds according to this invention therefore performsthe dual function of assisting in the formation of high tenacity fibresand films during the melt spinning operation and subsequently serves toprotect the spun fibre against oxidation at lower temperatures.

The following examples illustrate the invention.

EXAMPLE 1 To a series of 2 /2 g. samples of isotactic polypropylenegranules were added 25 ml. solutions in pentane of the followingcompounds, the concentration of the solutions being such as to depositon the granules by evaporation of the pentane 1.0 percent of theirweight of compound.

Compound A (DH (CHa)aC-OOH Compound B ()H (CH SiCH3--CH Compound 0 (|)H(CHa)aSiOH2 CH3 Compound D (1)11 oHmswm-Ootnsuortm I C(CH3)3 Compound E(I? CuH5NHC- The melt index of each of the treated samples was thenmeasured according to British Standard 2782, Part 1, 1965, Method Cusing a 2.16 kg. load, a reservoir temperature of 230 C. and a 0.0825in. orifice, the measurements being carried out at periods of 3 minutesand 13 minutes after introduction of the sample into the heatedreservoir. Each measurement of the quantity extruded through the orificewas taken over 0.5 minutes and the value obtained converted to give afigure for the prescribed 10 minute extrusion period. The melt index,that is the amount of polypropylene in grams extruded over a 10 minuteperiod, for each of the samples is given in the following table,together with a control measurement carried out on an untreatedpolypropylene sample.

Melt index Compound 3 min. 13 min.

Compounds A and E Were included for comparative purposes and the meltindex value for Compound A indicated that it was ineffective inassisting degradation of the polypropylene at 230 C. On the other handCompounds B, C and D all increased the melt index value significantlyand were at least as effective as Compound E which is a commerciallyavailable peptiser.

EXAMPLE 2 The compound (CH SiCH NH.C H was employed to treat two samplesisotactic polypropylene granules in the manner described in Example 1,the amount of compound deposited being 0.1 percent in. 9 12 d ld 1.0

percent in the other, each based on the weight of polypropylene.

Measurements of the melt index of the sample containing 0.1 percent ofcompound was performed after 3 minutes and 13 minutes. In the mannerdescribed in Example 1. Values of 2.8 and 5.0 were Obtained. Whensimilar measurements were performed after 3 minutes and 4 minutes on the1.0 percent sample values of melt index of 2.7 and 20.0 were obtained.When the compound was similarly tested at the 0.1% level for comparativepurposes melt index values of 2.3 and 2.6 were obtained after 3 minutesand 13 minutes respectively.

That which is claimed is:

1. A process for the production of a shaped article by the meltextrusion of thermally degraded isotactic polypropylene wherein thethermal degradation of the polypropylene is carried out in the presenceof from 0.01 to 5 percent by weight, based on the weight ofpolypropylene of (a) an organosilicon compound which is an organosilaneor organosiloxane having therein at least one siliconbonded group of thegeneral formula CH2NR2, wherein each R represents a hydrogen atom or amonovalent hydrocarbon radical, (b) an organosilicon compound of thegeneral formula wherein R, R" and R'" each represent a hydrogen atom, analkyl radical having up to 18 carbon atoms, an aralkyl radical having upto 18 carbon atoms or a Q SiCH group, wherein Q represents an alkyl,alkeuyl or aryl radical having up to 18 carbon atoms at least one of R,R" and R being the Q SiCI-I group, or (0) mixtures of (a) and (b).

2. A process as claimed in Claim 1 wherein the organosilicon compound(a) has the general formula wherein each A represents a radical havingfrom 1 to 18 carbon atoms inclusive and is a monovalent hydrocarbonradical, an alkoxy radical, an alkoxyalkyl radical, an alkoxyarylradical or an alkoxyalkoxy radical, n is 0, 1, 2 or 3 and R is ahydrogen atom amonovalent hydrocarbon.

3. A process as claimed in Claim 2 wherein each A represents an alkylradical having less than 9 carbon atoms or an aryl radical and n is 3.

4. A process as claimed in Claim 1 wherein each Q is an alkyl radicalhaving less than 9 carbon atoms or a phenyl radical.

References Cited UNITED STATES PATENTS 3,137,720 6/1964 Cooper 26045.7RX 3,296,190 1/1967 Rerschl et al. 260-] RX 3,419,653 12/1968 Briggs etal. 264- X 3,632,715 1/1972 Gowdy et al 264211 X JOSEPH L. SCHOFER,Primary Examiner W. F. HAMVICK, Assistant Examiner US. Cl. X.R.

26093.7, 94.9 GD, 43 Digest, 96 D, 94.7 D; 264-430, 170

1. A PROCESS FOR THE PRODUCTION OF A SHAPED ARTICLE BY THE MELTEXTRUSION OF THERMALLY DEGRADED ISOTACTIC POLYPROPYLENE WHEREIN THETHERMAL DEGRADATION OF THE POLYPROPYLENE IS CARRIED OUT IN THE PRESENCEOF FROM 0.01 TO 5 PERCENT BY WEIGHT, BASED ON THE WEIGHT OFPOLYPROPYLENE OF (A) AN ORGANOSILICON COMPOUND WHICH IS AN ORGANOSILANEOR ORGANOSILOXANE HAVING THEREIN AT LEAST ONE SILICONBONDED GROUP OF THEGENERAL FORMULA-CH2NR2, WHEREIN EACH R REPRESENTS A HYDROGEN ATOM OR AMONOVALENT HYDROCARBON RADICAL, 8B) AN ORGANOSILICON COMPOUND OF THEGENERAL FORMULA